Effect of Handle Design and Material on the Ergonomic Performance of a Dental Sickle Scaler

   

Olga Zozaya, Laura Bratt, Kalebi Shayo, and Amber Davis^*

Citation: Zozaya O, Bratt L, Shayo K, Davis A. Effect of Handle Design and Material on the Ergonomic Performance of a Dental Sickle Scaler. J Oral Med and Dent Res. 6(1):1-11.

Received: November 13, 2024 | Published: January 22, 2025                                                

Copyright^© 2025 genesis pub by Zozaya O, et al. CC BY-NC-ND 4.0 DEED. This is an open-access article distributed under the terms of the Creative Commons Attribution-Non Commercial-No Derivatives 4.0 International License. This allows others distribute, remix, tweak, and build upon the work, even commercially, as long as they credit the authors for the original creation.

DOI: https://doi.org/10.52793/JOMDR.2025.6(1)-87

Abstract

Background: Because musculoskeletal disorders (MSDs) are common among dental clinicians, there exists an urgent need to re-visit the design of dental hand instruments, which are considered a primary cause for work-related disabilities.

Objective: To evaluate in 11 hygienists, the effect of 4 different dental scaler handles on muscle work and fatigue related to a standardized scaling task using an SH 6/7 scaler.

Results: Overall, a silicone adaptive handle that conforms to the shape of the individual user’s hand demonstrated the most favorable ergonomic performance.

Conclusion: An adaptive silicone handle can significantly reduce muscle work and fatigue during scaling procedures.

Keywords

Dental Sickle Scaler; Musculoskeletal disorders; Handle Design

Introduction

Musculoskeletal disorders (MSDs) are considered to be one of the most prevalent occupational hazards for workers, only second to issues with the respiratory system [1]. MSDs can be attributed, in some cases, to trauma [2, 3]. However, the most common cause is repetitive activity, affecting muscles and surrounding structures, nerve endings, and vascular terminals [4]. The ultimate results include loss of functionality, pain, discomfort, lack of sensation, disability, and even external wounds [4].

The medical and dental fields are not exempt from MSDs [5]. Professionals such as general and reconstructive surgeons have a high incidence of occupational complications stemming from poor ergonomics and high workloads [6]. In dental offices, the intensity of work and the need for precision can lead to musculoskeletal injuries and extensive functional, social and financial burdens [7]. Dental hygienists are especially at risk for occupational injuries for several reasons: the need to adopt unergonomic postures to achieve adequate operative access, the daily use of repetitive small and precise motions requiring considerable force, and vibration from motor-driven tools [8]. In recognition of the musculoskeletal injuries experienced on a daily basis by hygienists, dental instrument design and materials are undergoing considerable re-evaluation to address the growing numbers of dental hygiene professionals who develop MSDs, especially carpal tunnel syndrome [9]. Variables under review include instrument diameter, texture, weight, and even temperature of the handle. [10] Surface electromyography (sEMG) techniques are being used to evaluate muscle work expended in different muscle groups during instrumentation with different handle designs and materials [2,14]. Other studies have characterized body ergonomics [2, 15,16], as well as grip and grasp strengths [10,18]. related to the use of different instrument designs and materials.

Additional research is urgently needed to identify and validate specific ergonomic instrumentation features that will improve the longevity of dental hygiene practitioners’ careers and reduce instrumentation-related pain, disabilities, poor work satisfaction and diminished quality of life from MSDs. The purpose of this study was to compare instrumentation-related muscle work and fatigue related to the use of 4 dental hand scalers with different handle designs and materials.

Materials and Methods

This study was reviewed and granted exempt status, as only de-identified, coded data were recorded during testing in typodont models.

Testers

Eleven first- and second-year dental hygiene students at Concorde Career College, Garden Grove were randomly selected out of a group of volunteers to participate in this study. Individuals with pre-existing conditions or symptoms within the last six months that might involve musculoskeletal injuries of the arms, fingers, wrists were excluded. All testers selected were right-handed for purposes of standardization. The aim in selecting dental hygiene students for this study was to eliminate the possible disparity in experience, routine, and neuromuscular accommodation between the rigid and adaptive test instruments, which might occur with more seasoned clinicians.

Protocol

In order to standardize the testing process as much as possible, each student utilized the same model of typodont (Kilgore 500HPRO, Kilgore International Inc., Coldwater, MI, USA), which was mounted to a dental unit. The tester and simulator were positioned in accordance with standard positioning guidelines, with the clinician adopting an ergonomic position sitting straight up, with the neck straight, the forearms parallel to the floor and knees at a slightly downward slope. Testers were instructed to change their own and the mannequin’s positions as needed in between each of the 1-minute instrumentation tasks, and to avoid re-positioning the typodont during the duration of the timed scaling task.

The four instruments included in this study were all fitted with SH 6/7 stainless steel blades (no sharpen-free technology used). The order of instrument use was randomized using the Research Randomizer software https://www.randomizer.org/. The instruments’ brand name was concealed with tape and labeled as follows: 1- stainless steel rigid; 2- resin rigid; 3- silicone rigid; 4- silicone adaptive. Nevertheless, testers could not be blinded effectively with regard to instrument identity because of the very different appearance and functionality of the curettes.

One designated clinician sharpened all the instruments between each use to ensure equal sharpness of the cutting edges during each study arm. Participants were instructed to scale each of the designated areas for 1 minute utilizing a light calculus removal stroke. The facial aspects, surfaces towards, of teeth #22-27 were scaled using the SH 6/7 sickles. Testers were given a 3- minute rest period between each testing arm. SEMG readings confirmed a return to baseline muscle activity before the begin of each new study arm.

Instruments

Four SH 6/7 sickles were evaluated, all with stainless/ no sharpen-free blades (Figure 1): Instrument A: conventional rigid stainless steel (Sterling®, Menlo Park, Gauteng, South Africa); Instrument B: conventional rigid resin (Paradise Dental Technologies, Missoula, MT, USA); Instrument C: rigid conventional rigid silicone (Iris 4696-500 0619, Benco Dental, Pittston, PA, USA); Instrument D: flexible silicone instrument (ErgoFlex®, DoWell Dental Products, Rancho Cucamonga, CA, USA) with universally adjustable, adaptive core that allows the instrument to adapt to the curvature of the hand and fingers.

Data collected included: (a) VAS questionnaires on a scale of 0 (best)-10 (worst) to evaluate instrumentation-related tester fatigue in thumb, fingers, palm and wrist; (b) sEMG traces to measure muscle work expended during instrumentation.

Figure 1: Four different types of scaler handles were tested in this study.

VAS Surveys and Open-Ended Comments

Standard physical visual analogue scale (VAS) surveys were used, as the information collected was of a subjective nature. The scores ranged from 1-10, and inputs were collected immediately after each instrumentation arm. Open-ended comments were also collected.

Surface Electromyography (sEMG)

Customized surface EMG (sEMG) electrodes (FREEEMG, ©BTS Engineering, and Quincy, MA, USA) recorded real-time, continuous action potential signals from 4 muscles that are specifically used for gripping and manipulating dental instruments [10]: Abductor Pollicis Brevis (APB), First Dorsal Interosseous (FDI), Flexor Pollicis Longus (FPL), and Extensor Digitorum Communis (EDC). These data were transmitted wirelessly to a Dell laptop via a USB-port dongle that connected with a proprietary FREEEMG software (BTS Engineering, Quincy, MA, USA) installed on a dedicated password-protected laptop computer.

Action potential data reflecting muscle activity were collected throughout instrumentation using standard techniques. First, live muscle function tests were performed to guide and fine-tune the placement of each electrode to an optimal position on each muscle (Figure 2) [19,10] Next, a commonly used approach that permits subsequent normalization of test data was implemented by asking the testers to perform 15 s of maximum voluntary isometric contractions (MVC) for each muscle [19,20]. This trace was then considered 100% activity for that muscle. Next, testers completed the prescribed scaling regimen. SEMG signals from all 4 muscles were recorded throughout instrumentation. For purposes of data extraction, the traces were rectified and filtered according to standard techniques by means of a second-order Butterworth filter while implementing a 10 Hz high-pass cutoff frequency. From the resultant integrated action potential graph, total workload was determined by calculating the area under the curve. All data evaluation was performed by a blinded pre-standardized investigator.